The Sun

Wow!

Many ancient peoples worshiped the Sun as a god. They thought a solar
eclipse meant the god was angry with them. They believed the Sun god's
anger could only be calmed with prayer and sacrifice.

The diameter of our closest star, the Sun, is 1,392,000
kilometers. The Sun is thought to be 4.6 billion years old. The Sun is a
medium size star known as a yellow dwarf. It is a star in the Milky Way galaxy
and the temperature in its core is estimated to be over 15,000,000 degrees Celsius.
In the Sun's core, hydrogen is being fused to form helium by a
nuclear
fusion process. The energy created by this process radiates up to the
visible boundary of the Sun and then off into space. It radiates into space in
the form of heat and light. Because the Sun is so massive, it exerts a
powerful
gravitational pull on everything in our solar system. It is because of the
Sun's gravitational pull that Earth orbits the Sun in the manner that it
does.

The Sun has several layers: the core, the radiation zone, the convection
zone, and the photosphere (which is the surface of the Sun). In addition,
there are two layers of gas above the photosphere called the chromosphere and
the corona. Events which occur on the Sun include
sunspots, solar flares,
solar wind, and
solar prominences. Sunspots are magnetic storms
on the photosphere which appear as dark areas. Sunspots regularly appear and
disappear in eleven year cycles. Solar flares are spectacular discharges of
magnetic energy from the corona. These discharges send streams of protons and
electrons outward into space. Solar flares can interrupt the communications
network here on Earth. Solar winds are the result of gas expansion in the
corona. This expansion leads to ion formation. These ions are hurled outward
from the corona at over 500 kilometers per second. Solar prominences are
storms of gas which erupt from the surface in the form of columns which either
shoot outward into space or twist and loop back to the Sun's
surface.

The Sun gives off many kinds of radiation other than light and heat. It also
emits
radio waves,
ultraviolet rays, and
X-rays.
The Earth's atmosphere protects us from the harmful effects of the ultraviolet
rays and the X-rays. The Sun does rotate, but because it is a large gaseous
sphere, not all parts rotate at the same speed. This is known as a differential
rotation.